The Alliance has fought its way into Earth’s solar system, only to find that the enemy Daleks have inexplicably terraformed the planet Jupiter. On Kalendorf’s orders, half of the fleet puts down for refuelling and shore leave, and Herrick sets engineering teams to work processing the planet’s mineral deposits. The second wave of enemy Daleks is lurking just off Venus’ orbit, and Kalendorf takes the opportunity of this lull to check up on the progress of Alliance gunship B68, which is soon to rendezvous with the mysteriously silent Defiant. But he has neglected his friend Mirana for too long for this concern to ring true to the Mentor, and she thus orders her monitor Daleks to conduct a thorough analysis of all of Kalendorf’s recent activity and find out what he’s trying to hide from her.

Initial reports from the engineers on Jupiter are almost too good to be true, and it hardly seems important when contact is lost with one perimeter guard patrol. But when contact is lost with a second patrol several hundred kilometres away after they call in to report a medical emergency, Herrick becomes concerned. He orders Sergeant Allenby and the 5th Airborne Division to split up and investigate both disappearances while he reports to Kalendorf, but by the time he makes contact with the flagship, ten different sections have gone off the air. It could be the result of a storm currently building up in the atmosphere, and Kalendorf thus agrees to try contacting the missing patrols and base camps from orbit.

Allenby’s team arrives in the area where perimeter guard 97 was on patrol, but there’s no sign of the missing soldiers or of any hostile life -- only cactus-like plants apparently swaying in the breeze. The soldiers fan out in search of their missing comrades, but one unlucky squaddie gets too close to one of the plants, is pricked by one of its thorns... and begins to change. Comms officer Sparks is reporting to Kalendorf when he hears the sound of gunfire outside, and something then bursts into the shuttle, kills Sparks and shoots out the comms unit. Kalendorf tries to contact base camp, but now even Herrick is off the air. Kalendorf orders all ships to evacuate from Jupiter immediately; it seems that they’ve walked into a trap after all...

Elsewhere, the Dalek Supreme receives a progress report. The Vaarga plants on Jupiter have begun their work, and when Kalendorf’s forces are destroyed, he will have no choice but to co-operate. But the Dalek Supreme remains cautious, and will not take action until he receives confirmation that Susan Mendes has been captured.

On the Defiant, Alby regains consciousness to find that he’s been locked up with Morli and Suz. Morli is relieved to see that Alby’s alive, and Alby is relieved when Suz wakes and reveals that she’s still herself. The Dalek Emperor’s consciousness remains dormant in her mind; the Daleks only woke it briefly to ensure that they hadn’t had a wasted journey. Suz and Alby have finally been reunited, but now the Emperor’s mind stands in the way -- and Alby fears that the Emperor put its mind into Suz’s body because it knew that she and Alby were in love, and that Suz, the legendary Angel of Mercy, was the one person it had access to who was most likely to be rescued. Suz wonders what good their love has done if it’s only given the Daleks another weapon to use against them...

Elsewhere, Mirana and Marber are drifting in their escape pod, desperately looking for some sign of Alby’s ship. They have no idea if they set off in the right direction in the first place, and they’re rapidly running out of fuel -- and when that goes, so will the air supply. Mirana holds out hope to the very last minute, but when the engines and oxygen shut down there is still no sign of Alby’s ship anywhere. Knowing they’re doomed, Marber asks Mirana to tell him what Kalendorf had planned, but Mirana admits that she asked him not to tell her, for fear that she wouldn’t like it. The stakes of this war are so high that Kalendorf would have to take inconceivable risks, and Mirana decided just to follow him blindly and leave the moral ambiguities to him. But quite some time ago she picked up an unidentified transmission from his flagship, and that gave her some nasty suspicions. As the air in the escape pod runs out and Mirana and Marber slowly asphyxiate, Mirana reveals her greatest fear: what if Kalendorf were to switch sides?

This story is all quite a lot for Siy Tarkov to take in, and he asks Saloran Hardew if she’s formed an opinion of Kalendorf. Is he really the monster of legend, the Dark One who brought about the Great Catastrophe? Saloran believes that Kalendorf was purely a warrior, one who was prepared to risk everything there was in order to win his war...

On Jupiter, defeat has been snatched from the jaws of victory, and Kalendorf is summoned before the Mentor to explain this devastating fiasco. The Mentor cuts through his efforts to explain and justify his actions, and reveals that although ships are currently launching from Jupiter’s surface, this is no evacuation. A close analysis of the planet, which Kalendorf should have conducted before he allowed his troops to land, has shown that the areas of lush vegetation are riddled with Vaarga plants, an animal-plant hybrid genetically engineered by the enemy Daleks on Skaro. Any humanoid pricked by the thorn of a Vaarga plant succumbs to its poison within minutes, transforming into a psychotic killer and eventually into another Vaarga. Worse, the plants on Jupiter have been subtly altered so that their victims develop a pack mentality. Half of Kalendorf’s fleet has just been transformed into an army of psychotic killers, and they are now attacking the other half.

Kalendorf begins giving orders to deal with the emergency, but the Mentor cuts him off in mid-sentence and relieves him of command. She has tolerated his individualism until now, but a detailed analysis of his actions over the past several years indicates the strong possibility that he’s been plotting with Alby Brook and Mirana to rescue the dangerous Dalek agent Susan Mendes. Kalendorf is to be brought to Lopra Minor for interrogation and “brain correction” -- and when he reveals that he knows of the Mentor’s related experiments in the Pkowik system, she realises that the research station’s destruction by enemy Dalek forces was no coincidence. Kalendorf neither confirms nor denies her allegations, and allows her Daleks to march him to the transport ship -- but the Courageous is attacked by Vaarga-infected humans, and in the ensuing confusion Kalendorf slips away from his captors, boards the transport ship alone and takes off. As the fleet falls into confusion behind him, he sets course for the Defiant -- and Suz.

Gunship B68 attempts to hail the Defiant, but the Alliance Daleks’ caution costs them their lives, as the enemy Daleks remain silent and then destroy the gunship as soon as it’s within weapons range. The Dalek Supreme has received their report on Susan Mendes, and is also aware that Kalendorf has ditched the Alliance fleet and is on his way. Confident that all is proceeding to plan, the Dalek Supreme orders his fleet’s second wave to attack and destroy the remains of the Alliance fleet around Jupiter.

Alby and Suz wonder what the Daleks have planned, and Alby tentatively suggests that Suz might be able to tell what the Emperor is thinking if its mind is dormant within hers. She explains that it doesn’t work that way, but then Morli speaks up; she’s been thinking, and has concluded that Suz had the right idea earlier when she threatened to kill herself. The enemy Daleks must be defeated, and can’t be permitted to get their Emperor back -- and that means Suz must die. Alby angrily reminds Morli that the Alliance Daleks aren’t any better, but she won’t listen, and it rapidly becomes clear that she was thoroughly brainwashed on the station in the Pkowik system. When Alby refuses to let Morli kill Suz, Morli overpowers him and prepares to kill Suz herself. Fortunately or unfortunately, the Daleks then arrive to escort their prisoners to the bridge, see what’s going on, and exterminate Morli.

Alby and Suz are taken to the bridge, where they learn that the Alliance fleet which seemed on the brink of victory is now being destroyed -- and that the Dalek commander is preparing for a rendezvous with Kalendorf. Kalendorf docks with the Defiant and is escorted to the bridge, where he refuses to act until the Daleks evacuate. The commander contacts the Dalek Supreme through its command net -- and, much to Alby’s shock, agrees to Kalendorf’s terms and transmats its team away to the approaching Dalek attack squadron. However, Kalendorf insists that there isn’t time to explain his plan; a second wave of Alliance vessels is approaching, as well as the enemy Dalek fleet, and the Defiant is caught in the middle. The rest of the Defiant’s crew is still alive in the loading bay -- the Daleks’ nerve gas only knocked them out -- and Kalendorf orders Alby to free them and barricade the airlocks. Alby points out that the Daleks have transmat technology and demands to know what Kalendorf’s really up to, but Suz insists him that she’ll be all right, and Alby reluctantly departs. But once Kalendorf and Suz are alone, Kalendorf makes telepathic contact with Suz, and she’s horrified to see what he has done -- and what he is planning to do. In order to defeat both Dalek factions, something terrible must happen...